it depends really. if he's a really good singer as well as lead guitarist, then just ask him if if it's okay for him not to play leads in every song. the majority of two gutarists in a band often alternate to keep their own playing entertaining. if he still is adament on doing both parts, then you could try composing intricate rhythms. or if he isn't that good of a singer, kick him out or find your own band. for me, when i'm in a band, the whole band needs to be on the same page, with simliar end goals in song writing. every one has to be enjoying what they are playing, and if any member isn't then that needs to be discussed and resolved. if however there are still problems, then a personel change may be needed, or as you said, hit him with your guitar!! lol!!